Pretty diffraction patterns

  • Thread starter p.tryon
  • Start date
  • #1
51
0
Hi
I was wondering whether anyone could suggest ways of making nice diffraction patterns using a red laser. I work at a charitable school in Kazakhstan so am limited in terms of materials. Any suggestions would be appreciated. Thanks
 

Answers and Replies

  • #2
189
0
What kind of diffraction patterns do you want to look at?

Do you have an old CD or DVD laying around? Bouncing a laser off of that, it acts as a diffraction grating.

You can use two razor blades mounted to make a nice single slit. You can even put a thin wire between them on one end, and make the blade edges touch at the other, and have a continuous variable width single slit.

I've seen double slits made with two razor blades and a thin wire.
 
  • #3
39
0
Turn the lights off in the lounge or kitchen etc .. and fire the laser beam at all sorts of stuff ..

Personally i like aiming at frosted or florescent light bulbs , but you will find all sorts of objects that work well in this regard (especially glancing angles where you aim at the edge of an object .
 
  • #4
189
0
Two more ideas. One that was done at my university and the photos featured in the Serway undergrad text...if you have a beam expander, make the beam larger than whatever small coin you have there. We generally use a penny or a dime, which are 9.25mm and 8mm in diameter, and are suspended by the thinnest thread we can find. When projected in a dark room, with a good expanded beam, you can see the shadow of the coin within the beam on a target some distance away. You will also see a bright spot in the CENTER of the target--a bright spot that can only be there because of diffraction. If it isn't clear, try moving the target closer or farther away--I don't recall the exact distance we used, but it was within an indoor laboratory.

Also, try stretching a hair straight and shining the laser on it. Try different hairs--see if the students can rank the hairs by thickness based on the diffraction pattern.

Use a piece of foil--even a candy wrapper--and make a tiny pinhole in it. I have made really small ones by placing the foil on a piece of glass, and tapping the pin on the surface of the foil. You'll see a circular aperture diffraction pattern--bright center spot, alternating dark/light rings.
 
  • #5
189
0
I found another I remembered--do you have a decent laser printer and transparency sheets that will work in it?

http://physics.bgsu.edu/~vanhook/gratings/ [Broken]
 
Last edited by a moderator:
  • #6
51
0
I love this site! Thank you so much for all these great ideas. I will try experimenting. The laser jet prints look amazing but I don't think we have the laser jet :-(

P.S. if we were investigating hair width based on the diffraction pattern is there an equation we would need?

Thanks again!
 
  • #7
39
0
I would investigate first without an equation if i was you p.t .
Bring forth equation from observation is a encouraging cycle .

Another thing to mention is that by reflecting the coherent bean obliquely off an object you can achieve a primary dispersion pattern ..

The secondary linear filtering of this pattern through a window can reduce the Photon beam considerably .. which can be interesting .

Also using some small electric fans as oscillating gates the beam can be further reduced in volume ..

cheers
 
  • #8
189
0
You could "calibrate" the hair-measuring laser setup by using wire of known thickness...maybe magnet wire. Measure the characteristics of the diffraction pattern with the various thicknesses of wire, look for a mathematical relationship between the pattern and the wire thickness, then interpolate or extrapolate to the thickness of the hair.
 

Related Threads on Pretty diffraction patterns

  • Last Post
Replies
15
Views
4K
Replies
2
Views
1K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
2
Views
685
  • Last Post
Replies
6
Views
7K
Replies
28
Views
3K
Replies
2
Views
2K
Replies
3
Views
4K
Replies
2
Views
635
Replies
16
Views
4K
Top